JPH11118838A - Ac voltage measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an AC voltage measurement device capable of measuring AC voltage more accurately by reducing the affection of a beat voltage produced when a turbulence voltage is mixed. SOLUTION: An AC voltage measuring circuit of a device which measures resistance by AC four terminal measurement structured so that it is provided with a phase detecting means 4, a low-pass filter 2, a digital converting means 7, and a measurement value calculation means 8. When a turbulence voltage is mixed in the AC voltage measuring circuit, in order to reduce the affection of a beat voltage generated when those values obtained by sampling measurement signals are averaged by a digital converting means 7, the frequency of the beat voltage is predicted beforehand, and the sampling cycle of the digital converting means 7 and a sampling period are set at a cycle of one per integer of the cycle of the predicted beat voltage and at a time of several times of integer of the cycle of the predicted beat voltage, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC voltage measuring apparatus using AC four-terminal measurement.

[0002]

2. Description of the Related Art In an AC four-terminal measurement used for measuring a resistance or an internal resistance of a storage battery, it is necessary to measure an AC voltage. A general method of measuring the AC voltage will be described with reference to the drawings.

FIG. 1 is a block diagram showing a general configuration for measuring the AC voltage. 1 is a voltage input terminal and 2 is a filter means. The filter unit 2 performs an operation of removing a DC voltage, an operation of removing high-frequency noise, and an operation of reducing a signal of a frequency component other than the measurement frequency with respect to the voltage input from the voltage input terminal 1. 3 is a phase detection means 4
In the AC four-terminal measurement, an AC signal having the same frequency and the same phase as the measurement current is used. The phase detection means 4 is generally used for a device for measuring a resistance or an internal resistance of a storage battery. The phase detector 4 outputs the output signal of the filter 2 as it is when the reference signal is positive, and inverts and outputs the output signal of the filter 2 when the reference signal is negative. Reference numeral 5 denotes a resistor, and reference numeral 6 denotes a capacitor. A low-pass filter is formed by 5 and 6, and smoothes a signal output from the phase detection means 4. Reference numeral 7 denotes digital conversion means, and reference numeral 8 denotes measured value calculation means. 9 is an input voltage of the phase detection means 4 and 10 is an output voltage of the phase detection means 4. Reference numeral 11 denotes an output voltage of a low-pass filter circuit formed by the resistor 5 and the capacitor 6, and also an input voltage of the digital conversion means 7.

When a signal in which a disturbance signal having a frequency component other than the measurement frequency is superimposed is input to the voltage input terminal 1, the filter means 2 removes or reduces the frequency component of the input signal other than the measurement frequency to reduce the voltage 9. Output to the phase detection means 4. The phase detection means 4 performs phase detection on the input voltage 9 and outputs a voltage 10. A low-pass filter circuit formed by the resistor 5 and the capacitor 6 smoothes the voltage 10 and outputs a voltage 11. The circuit constituted by the phase detection means 4, the resistor 5, and the capacitor 6 performs an operation of extracting only a signal having the same phase and the same frequency component as the reference signal from the signal output from the filter means 2, and outputting the signal as a DC voltage. Therefore, generally, the voltage 11 is a DC voltage, and has a DC voltage value corresponding to the AC voltage to be measured. The digital converter 7 converts the voltage 11 into a digital value and outputs the digital value to the measured value calculator 8. The measurement value calculation means 8 averages the measurement values input as digital values by arithmetic processing.

[0005]

However, in a storage battery or the like connected to a power supply device, since a ripple current is superimposed on the charging current of the storage battery, a ripple voltage of an integral multiple of the commercial frequency may be superimposed on the storage battery. There is a problem in that when measuring the storage battery, a beat occurs in the voltage 11 and the measurement value sampled by the digital conversion means 7 contains an error. Also, when a commercial power supply or the like is used as the power supply of the resistance measuring device, harmonics of the commercial power supply may be mixed into the circuit of the filter means 2 due to signal wraparound. There is a problem that the measured value generated and sampled by the digital conversion means 7 contains an error.

FIGS. 1 and 2 show the beat generation process described above.
This will be described using.

FIG. 2 is a diagram showing the waveforms of the voltages 9, 10, and 11 in FIG. 1 when a disturbance voltage having a frequency close to the measurement frequency is applied to the voltage input terminal 1.

When the internal resistance of the storage battery connected to the power supply is measured by AC four-terminal measurement, a measurement frequency is applied to a voltage input terminal 1 of a general AC voltage four-terminal measuring circuit shown in FIG. Other disturbance voltages are added together with the measured voltage. When a disturbance voltage other than the measurement frequency is applied to the voltage measurement terminal 1, the filter unit 2 removes or reduces the disturbance voltage other than the measurement frequency. However, when a disturbance voltage having a frequency near the measurement frequency is inputted, the disturbance voltage cannot be reduced by the filter means 2, and the measurement voltage on which the disturbance voltage is superimposed is inputted to the phase detection means 4. The waveform of the measurement voltage on which the disturbance voltage is superimposed has a beat-like waveform like the voltage 9 in FIG.

When a commercial power supply is used as the power supply of the resistance measuring device using the measuring circuit of FIG. 1, a harmonic of the commercial power supply may be superimposed on the filter means 2 due to a signal wraparound. The frequency near the measurement frequency cannot be reduced by the filter means 2, and the measurement voltage on which the disturbance voltage such as the voltage 9 in FIG.

[0010] The frequency of the beat of the voltage 9 is the frequency of the difference between the measured frequency and the disturbance frequency. When the voltage 9 is input to the phase detecting means 4, the operation of the phase detecting means 4 causes the output of the phase detecting means 4 to output a voltage waveform such as the voltage 10 in FIG. The voltage 10 in FIG. 2 is reduced by a resistor 5 and a capacitor 6 for high frequency components. However, the beat having a low frequency of the voltage 9 cannot be sufficiently reduced if the time constant of the low-pass filter formed by the resistor 5 and the capacitor 6 is small, and a beat waveform like the voltage 11 in FIG. 2 is output to the voltage 11 in FIG. Is done. In order to absorb the 11 beats shown in FIG. 2, it is necessary to increase the time constant of the low-pass filter formed by the resistor 5 and the capacitor 6. However, when the time constant is increased, there is a problem that the measurement time becomes longer.

When the voltage 11 on which the beat generated as described above is superimposed is sampled by the digital conversion processing 7, there is a problem that a measurement error occurs due to the voltage level of the beat voltage at the time of sampling.

[0012]

An AC voltage measuring apparatus according to the present invention is an AC voltage measuring circuit of a resistance measuring apparatus based on AC four-terminal measurement, comprising a phase detecting means, a low-pass filter, a digital converting means and a measured value calculating means. When the disturbance voltage is mixed in the AC voltage measurement circuit, the frequency of the beat voltage is predicted in advance in order to reduce the influence of the beat voltage generated when averaging the values obtained by sampling the measurement signals by the digital conversion means. Setting the sampling period of the digital conversion means to a period of an integer fraction of the predicted beat voltage period, and setting the sampling period to an integral multiple of the predicted beat voltage period. Features.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an AC voltage measuring apparatus according to the present invention, as a means for reducing the influence of a beat voltage generated when a disturbance voltage is mixed in an AC voltage measurement circuit, a state of occurrence of a disturbance voltage is predicted in advance. The frequency of the beat is estimated, and based on the estimation, sampling is performed by the digital conversion circuit at a timing that is an integer fraction of the cycle of the beat, and a time corresponding to an integral multiple of the cycle of the beat is sampled. The measurement error is reduced by averaging the measured values of. By doing so, the influence of the beat voltage generated when the disturbance voltage is mixed can be reduced, and more accurate measurement of the AC voltage becomes possible.

[0014]

An embodiment of the present invention will be described below.

FIG. 1 shows the configuration of an embodiment of the present invention. 1 is a voltage input terminal and 2 is a filter means.
The filter unit 2 performs an operation of removing a DC voltage, an operation of removing high-frequency noise, and an operation of reducing a signal of a frequency component other than the measurement frequency with respect to the voltage input from the voltage input terminal 1. Reference numeral 3 denotes a reference signal used in the phase detection means. In the AC four-terminal measurement, an AC signal having the same frequency and the same phase as the measured current is used. Reference numeral 4 denotes a phase detection means, which is generally used in a device for measuring the resistance or the internal resistance of a storage battery. The phase detector 4 outputs the output signal of the filter 2 as it is when the reference signal is positive, and outputs the filter 2 when the reference signal is negative.
Is inverted and output. Reference numeral 5 denotes a resistor, and reference numeral 6 denotes a capacitor. A low-pass filter is formed by 5 and 6, and smoothes a signal output from the phase detection means 4. Reference numeral 7 denotes digital conversion means, and reference numeral 8 denotes measured value calculation means. 9 is an input voltage of the phase detection means 4 and 10 is an output voltage of the phase detection means 4. Reference numeral 11 denotes an output voltage of a low-pass filter circuit formed by the resistor 5 and the capacitor 6, and also an input voltage of the digital conversion means 7.

As described above, when the measured voltage on which the disturbance voltage is superimposed is input to the phase detection means 4, the frequency of the beat voltage generated in the voltage 11 is f1, and the cycle of the beat voltage is T1.

FIG. 3 is a diagram showing a method of measuring a signal output to the voltage 11 according to the present invention. Reference numeral 12 denotes a waveform of the beat voltage, and reference numeral 13 denotes a measurement timing of the voltage 12. T2
Is the sampling interval. The sampling period of the digital conversion means 7 is a period that is a fraction of the expected beat voltage period, and the measurement timing 13 is set for each sampling period. The sampling time of the digital conversion means 7 is set to be an integral multiple of the expected beat voltage cycle, and the measurement value calculation means 8 performs averaging.

By adopting such a method, even if the first measurement timing is performed from any phase of the beat voltage 12, only a period of an integral multiple of the beat voltage 11 is measured at equal intervals. By averaging, the influence of the beat voltage 12 on the measured value can be reduced.

[0019]

As described above, according to the present invention, the influence of the beat voltage generated when a disturbance voltage is mixed is reduced,
There is an effect that more accurate measurement of the AC voltage becomes possible.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a general configuration for measuring an AC voltage in four-terminal measurement.

FIG. 2 is a diagram showing waveforms of respective parts of an AC voltage measurement circuit when a disturbance current is superimposed.

FIG. 3 is a diagram showing a measuring method according to the present invention.

[Explanation of symbols]

Reference Signs List 1 voltage input terminal 2 filter means 3 reference signal 4 phase detection means 5 resistor 6 capacitor 7 digital conversion means 8 measured value calculation means 9 input voltage of phase detection means 4 10 output voltage of phase detection means 4 11 5 and 6 Output voltage of low-pass filter circuit 12 beat voltage 13 measurement timing

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuo Takano 3-4-1 Shibaura, Minato-ku, Tokyo Grand Park Tower Inside NTT Tifa Facilities Inc. (72) Inventor Yuji Kawagoe 3-chome, Shibaura, Minato-ku, Tokyo 4-1 Grand Park Tower Inside NTT Tifiti Systems Inc. (72) Inventor Book Yes 3-4-1 Gram Park Tower in Minato-ku, Tokyo NTT Tifty Facilities Inc. (72) Inventor Katsuhiko Kozuka Grand Park Tower, 3-4-1 Shibaura, Minato-ku, Tokyo (72) Inventor Noboru Tanaka Inventor Noboru Tanaka 10-13 Minamimachi, Hanno City, Saitama Prefecture Inside Shindengen Kogyo Co., Ltd. 72) Inventor Kazuki Shinki 10th, Minamicho, Hanno City, Saitama No. 13 Shindengen Kogyo Co., Ltd. factory (72) Inventor Katsuhisa Michinaga 1 Kinoshoin Nishinosho Inono Babacho, Minami-ku, Kyoto Nippon Battery Co., Ltd.

Claims (1)

[Claims] 1. An AC voltage measuring circuit of a resistance measuring device based on AC four-terminal measurement, comprising a phase detecting means, a low-pass filter, a digital converting means, and a measured value calculating means, wherein a disturbance voltage is mixed in the AC voltage measuring circuit. In this case, the frequency of the beat voltage is predicted in advance and the sampling period of the digital conversion means is predicted in order to reduce the influence of the beat voltage generated when averaging the values obtained by sampling the measurement signals by the digital conversion means. An AC voltage measuring apparatus, wherein a period for performing sampling is set to an integral multiple of a cycle of a beat voltage, and a period for performing sampling is set to an integral multiple of a cycle of a beat voltage to be predicted.